Intelligent motor systems and control logic for creating heat with constant offset torque in stationary vehicles

Abstract

Presented are motor control systems, vehicles, and methods for generating motor heat while holding an offset motor torque during stationary vehicle operation. A method of operating an AC motor includes a resident or remote vehicle controller receiving a mode request to operate a vehicle in a stationary mode, and a temperature request including the AC motor generating motor heat during the stationary operating mode. The controller determines an offset motor torque to generate the motor heat and hold the AC motor's output member at a select position when operating the vehicle in the stationary mode. Using a DQ transform model of the AC motor, the controller selects multiple dq current trajectories located in respective dq operating quadrants of the DQ transform model based on the offset motor torque. The controller then commands a power inverter to transmit electrical current to the AC motor based on the select dq current trajectories.

What is claimed: 
     
       1. A method of operating an alternating current (AC) motor of a motor vehicle with a power inverter module (PIM), the method comprising:
 receiving, via a vehicle controller, a mode request to operate the motor vehicle in a stationary mode; 
 receiving, via the vehicle controller, a temperature request including a waste motor heat to be generated by the AC motor during operation of the motor vehicle in the stationary mode; 
 determining, via the vehicle controller, an offset motor torque to generate the waste motor heat and hold a motor output member of the AC motor at a select output position during operation of the motor vehicle in the stationary mode; 
 determining a direct-quadrature (DQ) transform model of the AC motor; 
 selecting, via the vehicle controller based on the offset motor torque, first and second dq current trajectories respectively located in distinct first and second dq operating quadrants of the DQ transform model; and 
 transmitting, via the vehicle controller to the PIM, a command signal to transmit electrical current to the AC motor based on the first and second dq current trajectories. 
 
     
     
       2. The method of  claim 1 , wherein selecting the first and second dq current trajectories includes:
 determining a maximum current magnitude for the AC motor; and 
 calculating the first and second dq current trajectories as projections in a plane of the DQ transform model based on the maximum current magnitude. 
 
     
     
       3. The method of  claim 2 , wherein determining the maximum current magnitude includes:
 receiving operating temperature data for the AC motor and/or the PIM; and 
 predicting the maximum current magnitude as a function of the operating temperature data and the select output position. 
 
     
     
       4. The method of  claim 2 , wherein the first and second dq current trajectories are respectively calculated as I dq1 =(I d1 , I q1 ) and I dq2 =(I d2 , I q2 ), where:
     I   d   =−I   ss *sin(β)
 
     I   q   =I   ss *cos(β)
 
     T   q =1.5 *PP *(λ d    I   q −λ q   I   d )
 
 where Tq is the offset motor torque; β is a current angle; I d  is a d-axis current; I q  is a q-axis current; 
 PP is a number of pole pairs in the AC motor; λ d  is a d-axis flux linkage; λ q  is a q-axis flux linkage; 
 and I SS  is a current magnitude. 
 
     
     
       5. The method of  claim 1 , further comprising:
 generating DQ reference frame voltage command signals based on the first and second dq current trajectories; 
 transforming the DQ reference frame voltage command signals to multiphase voltage command signals; and 
 determining a set of pulse-width modulation (PWM) control commands based on the multiphase voltage command signals, 
 wherein the command signal includes the set of PWM control commands. 
 
     
     
       6. The method of  claim 5 , wherein generating the DQ reference frame voltage command signals includes:
 determining reference frame feedback current signals based on measured three-phase reference stator currents fed back from the AC motor; 
 calculating a dq current trajectory error as a mathematical summation of the first and second dq current trajectories and the reference frame feedback current signals; and 
 calculating the DQ reference frame voltage command signals as time functions of steady state operation of the AC motor based on the dq current trajectory error. 
 
     
     
       7. The method of  claim 6 , wherein transforming the DQ reference frame voltage command signals to the multiphase voltage command signals includes an inverse transformation from a rotating orthogonal frame of the DQ transform model to a static three-phase reference frame. 
     
     
       8. The method of  claim 6 , wherein determining the set of PWM control commands includes generating a plurality of switching vector signals based on a duty cycle associated with a predefined PWM period. 
     
     
       9. The method of  claim 1 , wherein the command signal includes a pulse-width modulation (PWM) switching frequency derived by oscillating back-and-forth between the first and second dq current trajectories and the first and second dq operating quadrants of the DQ transform model. 
     
     
       10. The method of  claim 1 , further comprising:
 receiving, after transmitting the command signal to the PIM, measured three-phase reference stator currents fed back from the AC motor; and 
 transforming the measured three-phase reference stator currents to DQ reference frame voltage command signals. 
 
     
     
       11. The method of  claim 10 , wherein transforming the measured three-phase reference stator currents to the DQ reference frame voltage command signals includes an inverse transformation from a static three-phase reference frame to a rotating orthogonal frame of the DQ transform model. 
     
     
       12. The method of  claim 1 , wherein the motor output member includes a rotor shaft, the method further comprising receiving, via the vehicle controller, the select output position from an electronic position sensor attached to the rotor shaft. 
     
     
       13. The method of  claim 12 , further comprising determining an angular velocity of the AC motor as a derivative function of the select output position with respect to time. 
     
     
       14. A non-transitory, computer-readable medium storing instructions executable by one or more processors of a vehicle controller of a motor vehicle, the motor vehicle including an alternating current (AC) motor connected to a power inverter module (PIM), the instructions, when executed, causing the vehicle controller to perform operations comprising:
 receiving a mode request to operate the motor vehicle in a stationary mode; 
 receiving a temperature request including a waste motor heat to be generated by the AC motor during operation of the motor vehicle in the stationary mode; 
 determining an offset motor torque to generate the waste motor heat and hold a motor output member of the AC motor at a select output position during operation of the motor vehicle in the stationary mode; 
 determining a direct-quadrature (DQ) transform model of the AC motor; 
 selecting first and second dq current trajectories respectively located in first and second dq operating quadrants of the DQ transform model based on the offset motor torque; and 
 transmitting a command signal to the PIM to transmit electrical current to the AC motor based on the first and second dq current trajectories. 
 
     
     
       15. A motor vehicle, comprising:
 a vehicle body; 
 a plurality of road wheels attached to the vehicle body; 
 an alternating current (AC) motor attached to the vehicle body and operable to drive one or more of the road wheels to thereby propel the motor vehicle; 
 a battery pack attached to the vehicle body and operable to power the AC motor; 
 a power inverter module (PIM) electrically connecting the battery pack to the AC motor and operable to convert direct current (DC) power into alternating current (AC) power; and 
 a vehicle controller programmed to: 
 receive a mode request to operate the motor vehicle in a stationary mode; 
 receive a temperature request including a waste motor heat to be generated by the AC motor during operation of the motor vehicle in the stationary mode; 
 determine an offset motor torque to generate the waste motor heat and hold a motor output member of the AC motor at a select output position during operation of the motor vehicle in the stationary mode; 
 determine a direct-quadrature (DQ) transform model of the AC motor; 
 select first and second dq current trajectories respectively located in distinct first and second dq operating quadrants of the DQ transform model based on the offset motor torque; and 
 transmit a command signal to the PIM to transmit electrical current to the AC motor based on the first and second dq current trajectories. 
 
     
     
       16. The motor vehicle of  claim 15 , wherein selecting the first and second dq current trajectories includes:
 determining a maximum current magnitude for the AC motor; and 
 calculating the first and second dq current trajectories as projections in a plane of the DQ transform model based on the maximum current magnitude. 
 
     
     
       17. The motor vehicle of  claim 16 , wherein determining the maximum current magnitude includes:
 receiving operating temperature data for the AC motor and/or the PIM; and 
 predicting the maximum current magnitude as a function of the operating temperature data and the select output position. 
 
     
     
       18. The motor vehicle of  claim 15 , wherein the vehicle controller is further programmed to:
 generate DQ reference frame voltage command signals based on the first and second dq current trajectories; 
 transform the DQ reference frame voltage command signals to multiphase voltage command signals; and 
 determine a set of pulse-width modulation (PWM) control commands based on the multiphase voltage command signals, 
 wherein the command signal includes the set of PWM control commands. 
 
     
     
       19. The motor vehicle of  claim 15 , wherein the command signal includes a pulse-width modulation (PWM) switching frequency to oscillate back-and-forth between the first and second dq current trajectories and the first and second dq operating quadrants of the DQ transform model. 
     
     
       20. The motor vehicle of  claim 15 , wherein the vehicle controller is further programmed to:
 receive measured three-phase reference stator currents fed back from the AC motor after transmitting the command signal to the PIM; and 
 transform the measured three-phase reference stator currents to DQ reference frame voltage command signals.